Turbidity meter



July 13, 1943. J. KATZMAN TURBIDITY METER Filed Aug. 24, 1939 FIG. 4

v INVENTOR. JACOB KATZMAN ATTORNEYS Patented July 13, 1943 UNITED STATESPATENT OFFICE TURBIDI'I'Y METER.

Jacob Katzman, New York, N. Y.

Application August 24, 1939, Serial No. 291,695

2 Claims.

This invention relates to turbidity meters, that is, to means formeasuring the density of a colloidal suspension or of 'a solution forthe purpose of determining the clarity of the liquid and the relativeamount of foreign substances present therein.

In many industries and processes, the purity of a particular liquid usedtherein may vary under different conditions and in relation to its use.At a certain point in the process or use, the liquid, as for instance,oil or electrolyte or other liquids, may have developed suchcharacteristics owing to the precipitation of various components thereofor owing to changes or additions to the liquid of foreign matter as torender such liquid useless or impractical for the particular purpose.

The particular condition of the liquid can scarcely be determined byinspection. In various industries and uses, experimental methods havedetermined after what period of time a particular liquid may becomeimpractical for use and at such fixed intervals removal or replacementof the liquid is recommended. Where in particular cases the liquid maynot have become impractical for use at that particular time, then achange of the liquid will result in unnecessary waste; while inferiorproducts may result when a liquid in a particular instance may becomeimpractical for use within the time period set.

Analyzing the liquid for the purpose of determining the quality of theliquid at different periods is both impractical and inconvenient. It istherefore necessary to find a more practical and convenient method forimmediately determining at any particular moment what the specificquality of the liquid is.

Solutions or colloidal suspensions of different strengths as is wellknown, ofier differing resistances to the passage of light rays. Variousinstruments have been devised for the purpose of determining the densityof the solution or suspension by means of the impedance oii'ered by itto the passage of light. Such instruments have been inconvenient andcumbersome and it has been necessary to extract suflicient liquid fromthe vat or container used in the process and place such liquid in theinstrument for the purpose of determining the particular quality of theliquid.

In no case has an instrument been devised which will obviate thenecessity for removing a portion of a liquid from its container to theinstrument itself for testing. In no case has a convenient immersibleturbidity meter even been devised or used.

' provide a simplified means for comparing the turbidity, density orrelative presence of foreign substances in liquids. I

Other objects and uses of this invention will in part be apparent and inpart pointed out in the following specification and drawing, in which:

Figure 1 is a schematic view of a preferred form of my invention showingone method of transmission of the light through liquid to the comparisonelement.

Figures 2, 3, 4 and 5 are schematic views of modified forms of theinvention shown in Figure 1, showing different methods of transmissionof the light through the liquid.

Figure 6 is a schematic view of a modified form of my invention whereina direct comparison of the values of light transmitted through twodifferent media may be made.

Figure 7 is a fragmentary view of a modification of a portion of thestructure of Figure 6.

. Referring now to Figure 1, I have shown in schematic simplified forman arrangement whereby the resistance offered to the passage of light bya-liquid may be readily determined by immersion of one end of theturbidity meter into the liquid itself. The turbidity meter l0 comprisesa light source H and a photoelectric cell l2. The rays of light from thelight source ll are conducted by means of the tube l3 to the lightemission area I. The tube may be formed of quartz so that it will bendthe light rays to follow a desired path or may be formed of Lucite or itmay even be a hollow or solid glass tube suitably coated with areflecting surface and, if desired, an outer darkened protectivesurface. Where a hollow tube is used, then it may be necessary to coverthe light emission area I with a transparent light transmitting butliquid excluding medium. Obviously, any other suitable lighttransmitting means may be used which would cause the rays to issue fromthe area it.

The tube l5 likewise constitutes a light transmission tube preferably,although not necessarily, equal in properties and transmission tube l3.Tube I! has a light receiving surface 16 which will receive the lightrays from the light emitting surface H. A light ray striking the surfaceIt will be transmitted along the tube ii to the photoelectric cell II.The minute variations in the current induced in the photoelectric cellI! by variations or differences in the light received thereby will beregistered on a microammeter or galvanometer I! having a callbrated dial22.

It will thus be obvious that by means of the immersion of the turbiditymeter, 2. portion of the liquid to be tested automatically enters theregion I! between the light emitting and light receiving areas i4 and i6whereby the intensity of the light received by the area II will bevaried in accordance with the density of the liquid and the resistanceoffered by such liquid to the passage of light. Such variations in theintensity of the light will cause variations in the intensity of thecurrent generated by or through the photoelectric cell and willcorrespondingly cause variations in the indicating pointer of themicroammeter.

The ammeter may by proper experimentation be calibrated to be read notmerely in terms of the current transmitted, but in various grades,densities, or conditions of the liquid thus measured.

The entire turbidity meter ll may in special cases be a self-containedeasily portable unit, all the parts thereof being readily mountablewithin a single container; its size or at least the relative sizes ofthe tubes i3 and II and their casings I! being in cases of this typesuch that the end of the meter comprising the region it may be readilyimmersed in a restricted area, as, for instance, the oil tank of anautomobile. But while my inikntion makes such a portable arrangementpossible, it should be clear that the novelty of the instrument is by nomeans limited thereto. As a matter of actual practice, the lightemitting and receiving areas may be permanently fixed in the bath orelectrolyte and other members mounted in suitable relationship theretowhile the meter may be mounted outside the vat or in a supervisor'soffice or in any other suitable place. Such permanent arrangement may beparticularly desirable where continuous control is required of thecondition of the bath. Likewise, the parts may be arranged in asemi-permanent mounting, and the relative location or shape of themembers changed, the principal requirement being that the area ll beimmersible in the bath. This applies not only to. this particular formbut also to the other forms herein described.

As seen in Figures 2, 3, 4 and 5, this invention may take many variedforms all following the same principle, it being important in that theturbidity meter be immersible or immersed in any desired liquid, evenwhile said liquid is in use in a particular process,

As seen in Figure 2, the light source ill need not necessarily emit rayswhich are conducted into the liquid by a tube, but the light source mayactually be located in a tube II! which is either permanently ortemporarily immersed in the liquid, the rays from the light source thenbeing directed upon the receiving area H8 of the tube H5, the processthereafter being the same as that shown in connection with Figure 1.

It will be clear that in any of the embodiments each case the said Imeter giving an immediate and direct rea ng.

characteristics to the light marking which, of course, will notnecessarily be that for zero current.

The resistance should therefore be a variable one and a knob 2hr may beprovided extending outside of the casing in order to provide for thesimple adjustment of the resistance.

The source of current 2| may be batteries of various types, an ordinaryelectric outlet, or any other means which will activate the light sourcell.

Another embodiment of the same principle utilizing the same type ofapparatus but a slightly different type of light conductor is shown inFigure 4 wherein again the light source 2 may be immersed in the liquid,the light source being at the bottom or end of the tube 2 IS. The lightfrom the bulb 2 passes thru the glass partition 2, through any liquidwhich may be present in the region 2 l8 and is received upon the glasspartition 2|! and thereafter reaches the photoelectric cell 2l2, theoperation being exactly the same as that hereinbefore described.

Here again the entire meter may be encased in a single unit which may belight for ready portability, or parts thereof may be permanently fixedin the bath with the meter located at some suitable position; orsuitable mounting brackets may be provided for permanent orsemi-permanent mounting oi the member or members. In this form it ishelpful in order to obtain uniformity between different readings of thedensity I of the same liquid to make sure that the outer shell or casingis immersed so that the glass partition m is below the level of theliquid. In order to accomplish this result inthe case of a portableoutfit, a suitable mark may be made upon the outer shell or casing toguide the user.

In another form such as that shown in Figure 3, a reflecting surface 325may be utilized in the .outer shell or casing and built into the bottomthereof. The light from the bulb III is emitted through the glasspartition 3, striking the refleeting surface 325, is received throughthe glass partition lit, and impinges upon the photoelectric cell an,the operation again being exactly the same.

In this case also it is important to'so arrange the turbidity meter thatthe glass partitions Ill and ill are below the level of the liquid whenthe turbidity meter is in use, in order to obtain uniformity inreadings. For this purpose, a suitable mark may be made upon the shell.For permanent installations, the reflecting surface 82! may be mountedon or be a part of the bottom of the vat or a side thereof, the othermembers being suitably arranged.

In any of the instances shown in Figures 1-4 inclusive, as well as inFigure 5, the outer shell where it is used, may be so constructed 'as toprovide an opening therein so that the liquid may enter into the regionI! of, for instance Figure l or similar regions of the equipment shownin the other schematic diagrams so that a proper reading may be made.itbeing important that liquid fill the entire region between, forinstance, the surfaces I4 and II (Figure 1), Ill-H8 (Figshould be assmall as is consistent with rapid in-' flow and outflow of the liquidand preferably should be at the very bottom of the instrument to permitthe liquid to flow out readily after the test. To obviate errors due toexternal light in a meter which depends on light intensity attributableto a particular source or a comparison of light intensities, a shield orcover for the instrument may be provided to exclude outside lightsources as far as possible. For this reason, the perforation or place ofentry of the liquid will be preferably at the bottom of theinstrutowards the photoelectric cell 412 for purposes hereinabovedescribed. Except for the type of light transmitting medium used, theoperation is exactly the same as that described in connection with theprior figures.

This meter may be used in many and different ways. Thus for instance, intesting the quality of oil in an automobile, the meter may be calibratedin units showing the presence of ment so that the most dimcult possiblepath is provided for the entry of outside orrstray light.

In an enclosed tank or vat with a suitable opening for immersing themeter it is not necessary to consider this condition. In an open tank, asuitable shield or cover may be used.

In permanent or semi-permanent installation,

the depth of the vat or its conformation'may provide the desirableshielding effect; or the vat when built may have the instrument built asa part thereof.

Likewise, various other arrangements may suggest themselves forpermanent installations. Thus the light emission area may terminate neara side or the bottom of the vat; and a window may be provided in saidvat opposite such light emission area to transmit the light to thephotocell.

In ordinary use or for the usual instrument for ordinary purposes, themere placement of the entry for the liquid at the bottom of the meterwill be sufficient to exclude outside or foreign light at least to suchextent that it will not interfere appreciably with the readings.

Furthermore, it will be seen that where comparisons are made on the spotbetween a pure liquid and a liquid the turbidity of which may havevaried from the pure state, then, if the liquids are in similarcontainers, a comparison of the readings of the used and pure liquids ifmade under the same outside conditions, may nevertheless be accurate inspite of the entry of foreign undesired light into the light comparisonregion.

Where extremely delicate diiferences may be important however, theninstead of a simple opening through the shell l9 through which theliquid may enter, a tortuous path may be provided for the entry of theliquid, said tortuous path being coated with a light absorbing surfaceand having a sufficient number of bends to ex, clude any stray foreignlight which may be present.

As seen in Figure 5, this invention may be varied in many different wayswithout departing from the spirit thereof. Thus, instead of tubes orreflectors for guiding-the light lays the light source 4| i may be atthe bottom of the tube, its rays entering the prism 430, the prismbending the rays so that light is emitted from the surface 414 into theregion 8, passing therethrough and impinging on the surface 8 of theprism 43! and being bent thereby and directed impurities or in variousmarkings indicating good, fair or unusable. Or the meter may,immediately before being placed in the oil tank of the automobile beplaced in a small tank of similar conformation containing pure oil andthen a comparison between the readings may be made, it having previouslybeen determined by experiment what difference in readings willnecessitate a change in the oil.

Likewise in sewage disposal plants where the quality of the purificationwork at any particular time needs to be quickly determined. the metermay be placed in the inflowing current of sewage and a reading taken andthen it may be placedin the outflowing current of purified sewage and areading taken, the difference between the two readings showing theefficiency of the plant at any particular instant. For this purpose, apermanent or semi-permanent installation of two meters maysimultaneous1y,,on two indicators, give an immediate reading at anyparticular instant of the effectiveness of the process. Or a permanentor semi-permanent system such as that described in Figure 7. workingthrough two immersion members and two photocells may actuate a singlemeter to estab lish the effectiveness of the process.

Likewise, the meter may be used to determine the efficiency of the bathin various industrial applications such as electroplating, dyeing, etc.,where the quality and density of the liquid and the presence ofimpurities or other substances may immediately be determined.

In fact, by connecting the photoelectric cell to appropriate controlapparatus, the turbidity meter may actually be used to controlprocessessuch as electroplating or dyeing where variations ously causing a changein the flow of current. tend, through suitable amplifying apparatus orrelays, to control the process itself.

While there have been here described-"means whereby the turbidity of theliquid may be directly recorded upon the microammoter in terms of theintensity of the current generated by or through the photoelectric, celland means whereby, the microammeter being calibrated in suitableturbidity or other units, theturbidity of the liquid may be read offdirectly, other means for constructing and using the turbidity meterwithin the spirit of the present disclosure may readily be devised.

Thus, in the embodiment shown in Figure 6. there is provided a meanswhereby the original strength or setting of the light source isimmaterial and therefore a variable resistance such as 20 of Figure 1will be unnecessary. The light source may vary in intensity and in factthe light source if it comprises an ordinary bulb may be used until thebulb wears out and actually emits no further light. In this embsdimenfithe light from the light source 5 is d rected upon the ends 540 and 5Mof the tubes H3 and 542. The light source 5 may be located directlybetween the ends 540 and 54! or the light rays emitted thereby may beguided to the ends yvi I40 and ill of the tubes 2 and SIB. The tubes inthis embodiment may be constructed in the manner hereinbefore describedof quartz or Lucite or glass suitably coated and treated in the mannerhereinabove described in connec tion with Figure l.

The light transmitting tube 513 terminates in a light emitting area 5adjacent the region M8. The light emitted from the light transmittingarea .5 into the region 518 is received on the area 516 of the lightreceiving tube SIS and guided therefrom to the photoelectric cell M2.The light passing through the tube 542 is emitted by the lightemission'area 6 into the region 6l8 received upon the area SIB andtransmitted through the tube 543 to the photoelectric cell H2. Thephotoelectric cell 5}! is connected as in the manner shown in Figure lto the microammeter M1.

The light bulb an my be actuated in the manner shown in Figure 1 by asuitable source. As is hereinbefore pointed out, a suitable opening orperforation may be provided at the bottom of the shell or casing of theturbidity meter to permit the entry of liquid into the region 518.Where'the turbidity meter is to be used in the testing of one type ofliquid only at all times,

' then a quantity of pure unused liquid may be inserted in the meter inthe region BIS between the areas 6 and Eli and sealed therein againstdust and light, a simple small container being provided around theregion 6l8 to confine the liquid therein. The photoelectric cell 5|! maythen be plvotally mounted upon the turning axis 8 so that it mayselectively be turned towards the area 545 comprisirg the end of thetube SIS or towards the area 546 comprising the end of the tube 543. Asuitable knob 54! extendin outside the casing may be provided tofacilitate the turning of the photoelectric cell 5l2. Thereafter when itis desired to use the instrument, the light 5 is turned on by closingthe circuit (not shown) to the light source in any suitable manner, andthe photoelectric cell is by means of knob 5" turned towards the area516 where the light transmitted from the bulb 5 through the tube542through the pure liquid in the region 618 and through the tube 543 mayimpinge upon the photoelectric cell and the readingof the microammeter5| I then taken.

Thereafter'the photoelectric cell is by means of the knob 541 rotated.so that it faces the area 545 of the tube M5 and the light from the bulb5H passing through H3 and the liquid to be tested in the region SIB andthe tube 5l5 again impinges upon the cell. resulting in another readingof the microammeter 5H.

A comparison between these two readings will then give the relative turbdity'oi' the liquid tested. By this means. therefore, as long as thebulb Ill emits anylight at all, a true comparison may be madebetween thepure and impure liquids. contained in the region H8 is a permanent partof the instrument sealed therein against both light and dust.

Whatever the intensity of the light bulb, the comparison between thetworeadings will give the relative turbidity of the liquid being tested,and a suitable tablemaybe providedas an integral portion of the outershell of the instrument itself translating various diflerences intovarious turbidity values so that an immediate determi-- nation of thequality of the liquid being tested may result.

The small amount of the pure liquid The light comparison may, ifdesired, be made on an absolute basis, that is the region 8|. may not befilled with any liquid at all but may be simply sealed and closed sothat neither dust nor light may enter. Then the liquid entering in theregion H8 may be compared with an absolutely perfect condition whereinthe light in the region H8 is not interfered with at all by any liquid.In such case, a pure liquid will give a certain set or predetermineddiflerence and the difference will vary in accordance with the purity ofthe liquid.

This means may also be used in installations where immediate comparisonis desired between the liquids in two baths during a process. the

area 5" being immersed in one of the baths and the area 6 IS in theother.

In Figure 6 the tubes 2 and 543 are shown as of'a diflere'nt length fromthe tubes ill and H5. The relative length of the tubes is immaterial aslong as the tubes themselves do not absorb an appreciable amount oflight emitted by the light source ii I. If the instrument is tobe e!-tremeiy delicate in adjustment and ii it isto show minute diflerences,then in order to prevent the instrument from being inefllcient, thetubes l3 and 542 may be equal and the tubes 54! and 5!! may also beequal both in their length and other properties so that whatever lightabsorption or whatever changes in the characteristics of the light maytake place during its transmission from one point to the other, suchvariations will have no eilect upon the test itself; it should be noted,however, that the inequalities in the transmission of the lightmay becompensated in various ways, either by movement of the light source orthe photoelectric cell closer to the end of one or the other of thetubes, by the use of screens in any of the gaps or in any other suitablemanner. Also the tube ends ill and II should preferably be spaced aparta distance equal to that between the ends 6 II and 8 I. The instrumentshown in Figure 6 may be slightly varied to give a direct readingshowing the difference which in Figure 6 must be arrived at by a turningof the knob 5" and a comparison of the readings. That is, the apparatusmay be shown in Figure '7 wherein, instead of providing a singlephotoelectric cell 5l2, between the ends 545 and 546 of the tubes M5 and543, two photoelectric cells 5l2a and 2b may be provided therebetween.

Both of these photoelectric cells may be connected to the samemicroammeter 1a. The positive pole of photoelectric cell Mia and thenegative pole of the photoelectric cell Illb being connected to oneterminal of the microammeter liila and the negative pole ofphotoelectric cell 5|2a and the positive pole of photoelectric cell libbeing connected to the other terminal of the ammeter il'la.

It will thus be seen that the photoelectric cells are connected inopposition to each other and the microammeter 5I'la will show thediiference .between the intensities of the currents generated by thesephotoelectric cells. In this way, a direct comparison may be madebetween the pure liquid and the liquid to be tested and a direct readingshowing the quality of the liquid to be tested may be had. For thispurpose again it should be noted the light transmitting qualities oi thetubes leading to the area 548 should be equal to the light transmittingqualities of the tubes leading to the area 545 so that the diflerencesin the light paths themselves will not render the meter inaccurate, orsuitable adjustments may be made as herein described. And likewise thephotoelectric cells IIZa and H21) should also be equal in theirrespective qualities or suitable adjustments made so that whateverdifferences do occur shall be differences in light intensity resultingfrom the passage of the light through the liquid and from no othercause.

While this instrument has been described as applicable to thedetermination of the turbidity of liquids, it will be clear that it can,in suitable arrangements, test the qualities or density of gases andvapors, and even the air within a room or chamber as compared with thatelsewhere;

For this reason, the word fluid in the appended claims should be deemedto include liquids, gases and vapors.

It will thus be seen that my invention is capable of many and diverseembodiments and uses. I prefer, therefore, to be limited not by thespecific disclosures herein, but only by the ap pended claims.

I claim:

1. A turbidity meter for testing the turbidity of a liquid, said metercomprising a light sensitive medium and a light source; a lightconducting member having one end adjacent said light source and theother end immersible in said liquid for guiding the light emittedtherefrom through a predetermined amount of a liquid while said liquidremains in a container, and a similar member spaced by saidpredetermined amount from said first member for guiding the said lightfrom said liquid to said light sensitive medium;

said members being substantially parallel to and co-extensive with eachother; said light source and said light sensitive medium being disposedat corresponding ends of said members; the ends of said members definingsaid predetermined amount oiiliquid being remote from said light sourceandieaid light sensitive medium, and be; ing insertable into said liquidwhile said light source and light sensitive medium remain above thelevel oi said liquid; and means operable by said light, sensitive mediumfor determining the intensity of the emerging light; said last mentionedmeans being arranged to directly indicate the turbidity of said liquid.

2. A turbidity meter for testing the turbidity of a liquid while saidliquid remains in a container, said meter comprising a light source, aphotosensitive medium and means operable by said photosensitive mediumfor determining the intensity of light impinging thereon, and a lightconducting tube, one end of which is disposed adjacent said light sourceand the opposite end of which is remote from said first end anddisposabl within said liquid; and a second light conducting tube, oneend of which is remote from said first end and disposed adjacent saidphotosensitive medium and the opposite end of which is disposed oppositeand in proximity to the end of the first tube disposable in the liquidand spaced therefrom by a predetermined amount to define a predeterminedamount of liquid; said tubes being substantially parallel to andco-extensive with each other; said light source and said photosensitivemedium being disposed at corresponding ends of said tubes; the ends ofsaid tubes defining said predetermined amount of liquid being insertableinto said liquid while said light source and said photosensitive mediumremain above the level of said liquid; said light intensity determiningmeans being calibrated to indicate the turbidity of said liquids.

JACOB KATZMAN.

